Slide-valve of steam-enchnes



Stillle.

SAS

FIC

SLIDE-VALVE OF STEAM-ENGINES.

Specification of Letters Patent No. 25,952, dated November l, 1859.

-To all whom it may concern:

Be it known that I, NATHAN Corn, of Cincinnati, in the county of Hamilton and State of Ohio, have invented a new and Improved System of Side-Valves for Steam-Engines; and I do hereby declare that the following is a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming part of this specification, in which- Figure l is a longitudinal section of a slide valve with my improvement, and its seat and ports. Fig. 2 is a transverse section of the Fig. 3 exhibits the faceof the seat.

Similar letters of reference indicate corresponding parts in the several figures.

To enable others to make and use my invention I will proceed to describe its construct-ion and operation.

A, is the valve seat of the usual threeport kind, and intended to be inclosed or covered by a steam chest in the usual manner. a, a, are the steam ports, and the exhaust port arranged in the usual manner.

B, is the main valve made considerably longer and deeper than an ordinary slide valve would require to be for a similar three port seat in order that it may receive within it the eduction valve C, and be capable of the desired amount of motion independently of the latter valve, which is constructed, substantially like an ordinary main slide valve, that is to say with a similar exhaust cavity c, c, and with the two parts CZ, d, of its face which are at the ends, each wide enough to cover one of the steam-ports a, c. 'Ihe internal surface of the back c, of the outer or main valve B, and the external surface of the back f, of the inner or eduction valve are both made parallel with the faces of the valve and are fit-ted to work close together when the faces of the two valves work on the By the reciprocating motion which is given to the main valve B, by the eccentric gear, the said valve is made to uncover' the ports c, c, alternately to effect the induction of the steam, and cover them again to cut it off in a manner substantially the same as any other slide valve, but the interior of the said valve never communicates with the exhaust port Z), that always being covered by the eduction valve C. The main valve B, drives the leduction valve C, byl

the pressure of its ends against the ends of the said valve C, but the main valve being so much thelongest makes a considerable portion of its stroke without moving the eduction valve, and hence after the latter has, by the completion of the stroke of the main valve in either direction, been moved to a position to leave either port a, or a', wide open to the exhaust, it remains in the same condition while the .mai-n valve is returning to cut-o.

In Fig. l of the drawing the main valve is represented as having just completed its stroke to the right and to have opened the port a, to the steam, and, at the same time, to have moved the valve C, to a position to leave a, open to the exhaust, the crank rotating in the direction of the arrow shown upon it. The continued movement of the crank shaft and eccentric causes the main valve to return to cut off the steam, the cutting off being completed during a very small movement of the crank; and the main valve after having cut off steam will continue to move some distance before it commences to move the valve C. By properly proportioning the length of the valve B, to the length of C, and giving to B, a movement of proper length the steam may be cut off as early as one fifth of the stroke, and the exhaust be prevented completely closing till the piston has made nine tenths of its stroke, and this without giving the valve more than a desirable amount of lead. The arrangement represented for varying the stroke of the valve to vary the cut-off is by shifting the eccentric rods higher up or lower down the rocker I-I. This being a well known method of varying the cut-off with a slide valve needs no further description.

In the operation of the valves B, and C, the steam which enters between them from the cylinder after the supply from the steam chest to the latter has been cut off, forms a cushion to prevent concussion between the ends of the valves which need never obsolutely touch each other. To prevent too much steam being conned at either end grooves g, g, are provided in the interior of the back of t-he main valve B7 as shown in Fig. 2, and dotted in Fig. l, such grooves extending nearly to the ends of the said valve so that steam may pass freely from one end to the other till either end of the said valve B, arrives very near the end of the valve C, when steam is prevented passing between theuat surfaces of contact at the backs of the valves, and what remains between the ends of the valves is confined to form the cushion. Instead of grooves g, g, in the interior surface of the back of the main valve B, there may be grooves in the exterior surface of the back of the valve C, which would be equivalent to the grooves 9 9 ,To prevent the displacement of the inner valve C, by the sudden admission of steam to the interior of the valve B5 I provide notches 7L, h, shown in Figs. l and 3, in the inner edges of the ports a, a, to admit the steam from the cylinder to the said valve very gradually as the inner edges of the said valve pass those edges of the said ports shortly after the commencement of the movement of the valve in either direction. The da'nger of the displacement above mentioned arises from the peculiar action of the steam between the two valves which I will now describe, to wit: The steam never exhausts from between the valves but at each supply from the cylinder the loss of pressure which has taken place by the expansion in the cylinder is made up to the supply pressure. This admission of steam at a higher pressure acting at each end of the valve C, alternately is what would be liable to cause its displacement were it not for the provision which I have made to counteract it.

I do not claim broadly the use of a supplemental valve operating in combination with the main slide valve to prolong the eX- haust; nor do I claim providing a valve with a sliding seat for the same purpose.

What I claim as my invention and desire to secure by Letters Patent, is

The combination with the valves B, C, of the grooves g, g, and notches h, h, as and for the purposes set forth.

NATHAN COPE.

Witnesses:

W. CHIDsEY, SAMUEL Corn, CHAS. B. COLLIER. 

